By Dr. Harriet Burge

The MoldSCORE™ is designed to assist with interpretation of indoor/outdoor relationships with respect to spore trap data. Indoor and outdoor samples should be collected close together in both time and space.

Ideally, the samples should be collected simultaneously. Since this is often not possible, the best alternative is to do your walkthrough and decide where you will collect the indoor samples. Then find a place outdoors that is as close as possible to the primary entry of the space and collect a sample, followed by the indoor sample. This should be done for each indoor space sampled. If you can't collect that many samples, then you should collect an outdoor sample, then all the indoor samples, then a second outdoor sample.

So can you only do this in residential environments? Of course not. In a one-story office building or shop or bakery, or whatever, you can follow exactly the same directions. The problem comes when there are many storeys to the building. If there are balconies, or operable windows, you can collect the indoor sample, then go out on the balcony and collect the outdoor control. For operable windows, you also collect the indoor sample, then open the window and collect the outdoor sample just outside the window.

More difficult to interpret are indoor/outdoor data from buildings that have sealed windows. I have always climbed up onto the roof, found the air intake, and collected the outdoor control facing into the wind (i.e., with the orifice of the sample facing into the wind). As with residences, outdoor samples should be collected both before and after the indoor samples are collected.

Thinking about the effects of necessary changes in these protocols will help you with data interpretation. For example, if you can only collect one outdoor sample, but have sampled several different places indoors, you must consider the possibility that the outdoor sample is not really representative of all the outdoor samples. It may, in fact, be useful for only the first indoor sample.

Consider the proximity of the outdoor sample that you are able to take when interpreting MoldSCORE™ data. It may be that you can't collect a sample that is really near to a common entrance point to the space. In this case, be very careful to note the environment where the outdoor sample is taken. Are there potential sources that might skew the data? Actually, these notes should be taken for all outdoor samples.

Another thing to remember is that when you enter a space from outdoors you are taking the outdoor aerosol in with you. In large spaces (with many floors) this effect diminishes the longer you are in the space.

As an aside, if you are using indoor spaces as controls, ALWAYS collect the control samples first, and ALWAYS collect the same volume of air for both the test and control samples. If you sample in the most moldy part of a space first then go to an apparently clean space you will carry the mold along with you. If you collect more air in one or the other space, you will bias your comparison data because the limit of detection will be different.

As always, visual observation is essential and is the most important data that you can collect. If the inspection indicated no mold, but the MoldSCORE™ is high, then consider first whether or not a second, more thorough inspection would be prudent, or if the MoldSCORE™ could be incorrect. Likewise (or even more important), if the MoldSCORE™ is low in a case where there is visible growth, then your visual observations "trump" the MoldSCORE™. MoldSCORE™ is one of a variety of tools that can be used to help diagnose an IAQ problem.

This article originally appeared in the October 2010 issue of Indoor Environment Connections. Reprinted by permission.

Dr. Harriet Burge

Director of Aerobiology

Dr. Harriet Burge is EMLab P&K's Director of Aerobiology and Chair of EMLab P&K's Scientific Advisory Board. Widely considered the leading expert in indoor air quality (IAQ), Dr. Burge pioneered the field more than 30 years ago. She has served as a member of three National Academy of Sciences committees for IAQ, including as Vice-Chair of the Committee on the Health Effects of Indoor Allergens.

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